1. Field of the Invention
The present invention is directed generally to an arrangement for controlling or regulating the emission wavelength and emitted power of a semiconductor laser.
2. Description of the Related Art
Laser diodes which have a stable or regulable emission wavelength or a constant emitted optical power are needed in numerous applications of semiconductor laser diodes. For example, such diodes are used in wavelength-division multiplex applications, and in particular in those having narrow channel spacings, and they are also used in optical frequency-division multiplexing or in optical heterodyne reception.
For transversely and longitudinally monomode laser diodes, examples of which are distributed feedback (DFB) or distributed Bragg reflector (DBR) lasers that are presently available, small shifts in emission wavelength are caused by temperature drift, changes in threshold current, and degradation. Such shifts, for example, result in operational disturbances as a result of their interaction with narrow-band optical filters. Furthermore, such laser diodes vary in their optical output power as the result of aging.
Up until now, stabilization or regulation of the emission wavelength of semiconductor lasers has been successful only when complicated arrangements are used to provide external resonators and extreme temperature stabilization. Such arrangements are not suitable for integrated optical arrangements and are not adequate in their degree of stabilization.